diff --git a/libmpdemux/mpeg_hdr.c b/libmpdemux/mpeg_hdr.c
index 8376fbaeda..3e4bbfe31b 100644
--- a/libmpdemux/mpeg_hdr.c
+++ b/libmpdemux/mpeg_hdr.c
@@ -26,7 +26,7 @@ static float frameratecode2framerate[16] = {
 };
 
 
-int mp_header_process_sequence_header (mp_mpeg_header_t * picture, unsigned char * buffer)
+int mp_header_process_sequence_header (mp_mpeg_header_t * picture, const unsigned char * buffer)
 {
     int width, height;
 
diff --git a/libmpdemux/mpeg_hdr.h b/libmpdemux/mpeg_hdr.h
index e38b244e3b..b5a189c5a5 100644
--- a/libmpdemux/mpeg_hdr.h
+++ b/libmpdemux/mpeg_hdr.h
@@ -20,7 +20,7 @@ typedef struct {
     int picture_type;
 } mp_mpeg_header_t;
 
-int mp_header_process_sequence_header (mp_mpeg_header_t * picture, unsigned char * buffer);
+int mp_header_process_sequence_header (mp_mpeg_header_t * picture, const unsigned char * buffer);
 int mp_header_process_extension (mp_mpeg_header_t * picture, unsigned char * buffer);
 float mpeg12_aspect_info(mp_mpeg_header_t *picture);
 int mp4_header_process_vol(mp_mpeg_header_t * picture, unsigned char * buffer);